The present invention relates to controls for gas valves, and more particularly to an adjustable relay control having three-stage operation for regulating flow through a gas valve.
Most homes today use a single stage heating, ventilating and air-conditioning (HVAC) system for controlling climate conditions within the homes. With respect to heating, when in heating mode, these systems are either full xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d depending upon user-defined settings provided to a thermostat, which controls operation of the HVAC system. Thus, the system will provide either high heat, when heat is needed, or no heat when the particular user defined temperature settings have been satisfied. The problem is that the system provides only one mode of operation, which is not very economical. These single stage systems do not distinguish between a condition when the difference between the actual and desired set-point temperature is small (i.e., low heat is needed), and when that difference is large (i.e., high heat is needed). Thus, not only is energy wasted (i.e., high heat is activated even if the temperature difference is small, oftentimes resulting in xe2x80x9cover-shootingxe2x80x9d the desired temperature), but every time the system is activated, the blower fan is turned on xe2x80x9chighxe2x80x9d with a noticeable level of noise to occupants of a home.
More economical systems were developed and are known that provide two-stages of operation. Therefore, depending upon the temperature demands as determined by a thermostat, the system provides heat at either a high level or low level. For example, if the thermostat is set such that during the day the home is kept cooler (i.e., temperature is set-back while occupants of house are at work), when the system demands heat later in the day, prior to the occupants returning, to satisfy the thermostat settings, high heat is provided to rapidly warm the home (i.e., gas valve of the heating system provides full flow and blower fan is high) until the room temperature is near the desired set-point temperature. Thereafter, the second-stage provides low heat (i.e., the gas valve of the heating system provides low flow and the fan blower is low), and will continue to do so each time a small deviation from the actual temperature occurs and a demand for heat is made. Thus, the system is both efficient in high heat stage, and economical in low heat stage. Additionally, the low heat stage is much more quiet in operation than the high heat stage. However, because the high heat stage operates until room temperature is near the set-point temperature, the cost of operation (i.e., gas cost) is not greatly reduced. Also, the system still operates at full heat until the set-point temperature is almost met, thus resulting in noticeable operating noise (i.e., fan blower operation) during most of the heating system""s operation period and possible over-shoot in temperature.
What is needed is a system that allows for adjustable operation in multiple stages, which not only reduces operating costs, but minimizes operating noise. The present invention solves these needs by providing a system that includes three-stages of heating: a low heat operating level (low gas flow level and blower is at low speed), a high heat operating level (full gas flow level and blower is at high speed) and a mid-heat operating level (mid-flow of gas and blower is at intermediate speed).
Essentially, the present invention provides a three-stage relay control for regulating gas valves at three levels of operation (i.e., three different outlet gas levels or pressures). However, although the present invention will be described in combination with a gas valve for a furnace, it should be appreciated that the present invention may be used in conjunction with other gas devices, such as boilers, space heaters, water heaters, log flame valves and clothes dryers, to name only a few other applications.
More specifically, the relay control of the present invention preferably controls the operation of the servo-regulator of a gas valve and may be operated at three energy levels: off, middle and high. A solenoid or coil of the relay control is energized in one of these three energy levels depending upon the heating demands of the system.
A control arm that is part of the relay control pivots as a result of a magnetic field generated by the coil, and operates in conjunction with a plurality of adjustment screws and the servo-regulator, to regulate the level of gas flow at the gas valve outlet. Thus, the rate of gas flow is provided at three different stable levels. Preferably, a low-flow adjustment screw, a mid-flow adjustment screw and a high-flow adjustment screw are provided to set the desired opening of the gas valve in each of the three flow states. Additionally, a biasing or control spring is also provided in connection with the control arm to provide proper gas valve operation in each of the three stages.
While the principal advantages and features of the present invention have been explained above, a more complete understanding of the invention may be attained by referring to the description of the preferred embodiments which follow.